<i>Chandra</i> revisits WR 48a: testing colliding wind models in massive binaries

We present results of new Chandra High-Energy Transmission Grating (HETG) observations (2019 November - December) the massive Wolf-Rayet (WR) binary WR 48a. Analysis these high-quality data showed that spectral lines in this are broadened (FWHM = 1400 km/s) and marginally blushifted (~ -100 km/s). A direct modelling high-resolution spectra framework standard colliding stellar wind (CSW) picture provided a very good correspondence between shape theoretical observed spectra. Also, line profiles most cases an acceptable representation ones. applied CSW model to X-ray 48a from previous observations: Chandra-HETG (2012 October) XMM-Newton (2008 January). From expanded analysis, we find emission WR48a is variable on long timescale (years) same valid for its intrinsic emission. This requires mass-loss rates over orbital period. The absorption (in excess winds binary) as well. note lower accompanied by higher absorption. qualitative explanation could be presence clumpy non-spherically symmetric may play role.